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Factcheck: What’s the significance of a record high in Antarctic sea ice?

07 Jul 2014, 16:20

Roz Pidcock

Sea ice around Antarctica is growing, and it's a
scientific puzzle. But while the Mail on Sunday suggests this means
climate change is less of a problem than scientists say, sea ice is
only part of what's going on in Antarctica, and the world as a
whole is losing ice rapidly.

This follows news last week from scientists at the
University of Illinois that the area covered by sea ice surrounding
Antarctica hit a
record high on 29th June, with about two million square
kilometres in June more ice compared to the long term average.

Antarctic sea ice reached a record high in
June, with 2.1 million square kilometres more than the long term
average. Source: US National Snow and Ice Data Centre (
NSIDC)

Some parts of the media have chosen to put a
very positive spin on the news, giving the impression climate
change may not be as grim as scientists' projections after all. In
theMail on Sunday, journalist and climate
skeptic David Rose says:

"The levels of Antarctic sea-ice last week hit
an all-time high - confounding climate change computer models which
say it should be in decline..."

A separatearticleby climate-skeptic blogger Andrew
Montford suggests the rise in Antarctic sea ice has come as a
surprise to climate scientists, and claims it's "another mishap to
tarnish the credibility of climate science".

So has the sea ice growth left science in
disarray, as the Mail on Sunday suggests?

Not really. Scientists are up-front about the
fact that they don't fully know why Antarctic sea ice is growing,
and as far as the significance of changes in sea ice goes from the
point of view of climate change, a global look reveals that the
planet is losing ice, fast.

Sea ice on the rise (but only in
Antarctica)

Despite rapidly warming water, the amountof ice that floats on the
Southern Ocean around Antarctica - known as sea ice - has been
increasing by1.5 per centon average per decade since
1979.

Scientists don't yet fully understand why. But
an earlierarticlein Saturday's Daily Mail
by Ellie Zolfagharifarddoes a good job
of examining how in the Antarctic, warmer ocean temperatures could
actually lead to more sea ice. The piece features quotes by Dr Mark
Serreze, director of the National Snow and Ice Data Centre (NSIDC),
who says:

"Scientists believe the
shift is caused by water melting from beneath the Antarctic ice
shelves and refreezing back on the surface."

But that's just one explanation. A piece in
Saturday'sTimesgives a good overview of other
theories about how localwindpatterns may be involved. For more
detail, the US National Snow and Ice Data Centre have produced a
useful briefing on Antarctic sea ice,here.

The world is losing ice overall

The two poles are in quite different situations.
While the Antarctic is a land mass surrounded by ocean, the Arctic
is an ocean with land around the outside.

Arctic sea ice is in long term decline, reaching a
record low in September 2012. Source: NSIDC

In September 2012, Arctic sea ice reached
itslowest extentsince satellite records began
in 1979. While Antarctic sea ice is growing by on average165,000 square kilometresper decade, this
is dwarfed by the loss of an average of 480,000 square kilometres
per decade from the Arctic.

The Times and Saturday's Daily Mail articles
both pick up on this comparison, the latter featuring a quote by
polar scientist Walt Meier explaining why Antarctic ice growth is
less significant a measure than declining Arctic sea ice coverage
when assessing climate change. He says:

"While the
Arctic has seen large decreases through the year in all sectors,
the Antarctic has a very regional signal - with highs in some areas
and lows in others."

In other words, there are fewer factors
affecting ice behaviour in the Arctic, so what's happening there
can be more directly linked to long term changes in ocean
warming.

In the Mail on Sunday, Rose mentions that the
Arctic is losing sea ice but doesn't say how the size of the long
term trend compares to the observed gain in the
Antarctic.

Montford argues that "across the globe, there
are about one million square kilometres more sea ice than 35 years
ago".

Right now, it's true here is about one million
square kilometres more sea ice globally than the long term
average,as the red line in the graph below
shows.

But this uptick is the result of a couple of
record years for sea ice in the Antarctic - for most of the past 35
years, global sea ice has been in decline.

Scientists suggest that as temperatures rise in
the Antarctic, sea icewon't be ableto re-freeze quick enough to
keep pace with the amount being lost from under the ice
shelves-meaning Antarctic sea ice will
decline and the loss in total sea ice cover will become more
pronounced.

Since scientists don't yet fully understand why
Antarctic sea ice is growing, models haven't been able to predict
the increase. Montford suggests this is "something of an
embarrassment for climate modellers, making them reluctant to talk
about it."

In fact, it's an area of active research for
scientists, as Rose's article points out the recent report from the
Intergovernmental Panel on Climate Change (IPCC) discussed the
issue in great detail, concluding:

"Most models simulate a
small downward trend in Antarctic sea ice extent … in
contrast to the small upward trend in observations … There is low
confidence in the scientific understanding of the small observed
increase in Antarctic sea ice extent due to the incomplete and
competing scientific explanations for the causes of change and low
confidence in estimates of natural internal variability in that
region".

It's also worth noting that the rapid loss of
ice in the Arctic has also occurred faster than three quarters of
climate models predicted - a point also discussed in the IPCC
report, but which Rose and Montford neglect to mention.

While the growth in Antarctic sea ice has
scientists searching for explanations, it's only part of the
picture of global sea ice - and we're not aware of any scientists
who would argue that growing Antarctic sea ice offers a reason to
rethink their overall scientific understanding of climate
change.